An expectation is a projection or forecast about when or where an upcoming event will occur or what an upcoming event will be. Evidence suggests that the infant's capacity for expectations changes markedly between 6-9 months. The long-term objective of the present work is to explore the human infant's development of expectations about the time when an event will occur, the location where an event will occur, and the identity of the upcoming event. Development along these dimensions creates expectations that are more firmly vertebrated (i.e., organized or constructed in an orderly or developed form), or perhaps, more computationally complex (i.e., based upon multiple, interacting dimensions) Three experiments are described that use the visual expectation procedure developed by Haith and his colleagues and the cue-target procedure developed by Posner and Rothbart to assess expectations about the timing, location, and identity of upcoming events in infants at 3, 6, 9, and 12 months. Each experiment is designed to measure a single aspect of expectation through the use of three separate procedures that should be sensitive to that aspect. Each infant will be tested in all three procedures so that an aggregate score can be calculated at each age. Analysis within each experiment will explore the development of specific aspects of expectation and analysis between the experiments will address issues of cross-aspect continuity or independence. The health relatedness of the project is that an understanding of the infant's expectations and how to measure them may provide a window on cortical functioning and malfunctioning and is thus relevant for descriptions of normal development and for the diagnosis of trauma (e.g., closed head injury) and diseases with frontal involvement (e.g., PKU). A small sample of infants with early-treated PKU will be tested with the procedures developed here.